Acoustic apparatus



Feb. 9, 1965 p. R. WILSON ACOUSTIC APPARATUS Filed Jan. 20, 1964 FIGS INVENTOR DONALD R.WILSON BY new A LNT United States Patent 01 3,168,934 ACOUSTIC APPARATUS Donald R. Wilson, Santa Cruz, CaliL, assignor to Pacific Plantronics, Inc., Santa Cruz, Calif., a corporation of California Filed Jan. 20, 1964, Ser. No. 338,756 Claims. (Cl. 181-31) This invention relates to light weight sound translating apparatus which uses acoustical ducts to transmit desired sounds to a remote transducer and which includes ports at the inlet end of the acoustical ducts that reduce the effect of ambient noise accompanying the desired sounds.

Conventional microphones are commonly placed in front of the speakers mouth to pick up the desired sounds at very high levels relative to the level of background noise. One disadvantage encountered in operating a microphone in this position is that air and wind noise caused by impinging breath is picked up at high levels with the desired sound.

Accordingly, it is an object of the present invention to provide a microphone located away from the speakers mouth which picks up the desired sound through acoustical ducts having an inlet disposed at or near the corner of the speakers mouth.

It is another object of the present invention to provide inlet ports for acoustical ducts which reduce the effect of ambient noise transmitted with the desired sound along ducts to a remotely located transducer.

It is another object of the present invention to provide means for acoustically balancing two ducts of apparent dissimilar lengths.

In accordance with the illustrated embodiment of the invention, a pair of acoustical ducts transmit sound from a source to a remote transducer. An inlet port for one duct is positioned near the source of sound as, for exampie, the corner of a speakers mouth and an inlet port for e the other duct is positioned away from the source of sound. Noise and voice received by the inlet port near the speakers mouth is combined at the remote transducer with the noise only received by the inlet port positioned away from the speakers mouth. The noise signals in both ducts arriving at the transducer inphase are substantially canceled while the voice signal in one duct only arriving at the transducerproduces a high level output signal.

Other and incidental objects of the present invention wiil be apparent from a reading of this specification and an inspection of the accompanying drawing in which:

FlGUREl is a pictorial diagram of the transducer and acoustical ducts in position about themouth of a speaker;

FIGURE 2 is a schematic diagram of the acoustical ducts attached to a transducer;

FIGURE 3 is a sectional view of the tip showing the construction of the inlet-ports; and

FIGURE 4 is a sectional view of a tip according to another embodiment of the invention.

Referring to FIGURE 1, there is shown a transducer such as a microphone 1 connected through acoustical ducts 2 to the tip 5 located near the corner of the speakers mouth. The tip 5 includes a noise and voice inlet port 4 located near the mouth and a noise inlet port 3 located away from the mouth.

FIGURE 2 shows the construction of the inlet ports and acoustical ducts. The noise inlet port 9 positioned away from the speakers mouth is connected to one duct 7 through a reverse turnll. The acoustical equivalent of this reverse turn 11 is a length of duct 12 normal to the noise and voice inlet port 10 which connects the port 10 with duct 8. This acoustical equivalent 12 of the reverse turn 11 equalizes the effective lengths of the ducts 7 and 8, thereby minimizing relative phase shifts of acous- 3,168,934 Patented Feb. 9., 1965 tical signals in the ducts. Noise signals from background sources entering ports 9 and 10 thus arrive at the transducer 6 in phase and at substantially equal acoustical levels. These noise signals are applied to opposite sides of diaphragm 6a and thus are canceled out producing no electrical output on coil 6b. Voice signals entering port 10 appear in duct 8 at much higher acoustical levels than voice signals entering port 9 and appearing in duct 7 because of the proximity of port It) to the voice signal source. These voice signals thus do not cancel at trans ducer 6 but rather excite the transducer to produce a substantial electrical output.

In the embodiment shown in FIGURE 3 the tip includes an outer wall 2t) surrounding the acoustical ducts 13 and 14 to form a voice and noise inlet port 16 and a noise inlet port 15. An acoustical separator 17 disposed about the ducts 13 and 14 and Within the wall 20 includes a radially extending passage for each of the ducts and a horizontal passage 18, 19 connecting a radial passage and an inlet port 15, 16. The passages in the acoustical separator 17 thus provides the reverse turn 15, 18, 14 and its acoustical equivalent 16, 19, 13. The dimensions of the radial and horizontal passages in the acoustical separator 17 are so chosen that sound waves in these passages propagate essentially parallel to the walls of the passages and thus lose the ability to sense the original direction of propagation before making a turn. The ends or" ducts 13 and 14 are sealed by plugs 21.

FIGURE 4 shows another embodiment of the present invention in which the reverse turn 27 and its acoustical equivalent 23 are formed as passages within the tip 26 which connect the noise inlet port 24 and the voice and noise Inlet port 25 to the acoustical ducts 23 and 22, respectively.

I claim:

1. Acoustical apparatus comprising:

a pair of acoustical ducts of similar length, each having first and second ends;

a sound-receiving tip of elongated shape attached to said acoustical ducts, said tip having a longitudinal axis aligned with said ducts and having a pair of inlet ports disposed at opposite ends thereof along said axis;

a first passage in said tip extending transverse to said axis and connecting one inlet port and the first end of one of said ducts;

a second passage in said tip extending transverse to said axis and connecting the other inlet port and the first end of the other of said ducts;

the acoustical length of said one inlet port and first passage being equal to the acoustical length of said other inlet port and second passage; and

a transducer connected to the second end of said ducts for producing output signals related to the combination of acoustical signal appearing in said ducts.

2. Acoustical apparatus comprising:

, a pair of acoustical ducts, each having ends;

.one end of one of said ducts being positioned back aiong said one duct;

' the other of said ducts having an olfset bend near the corresponding end thereof the portions of said other duct on opposite sides of the offset bend being substantially parallel at a point along said duct intermediate the ends thereof; and

an electrical transducer connected to the remaining 7 means disposed near said element for producing electrical signals in response to movement of said element; and

means connected'to said ducts for applying the acoustical signals therein to opposite sides of said element;

4. Acoustical apparatus comprising: 'a pair or acoustical ducts of similar length, each having first and second ends; 7

a signal-receiving tip including an outer element having an opening therethrongli disposed to encircle the first ends of said ducts and a portion of the length of said ducts for providing an aperture between said ducts and the outer element; 7

a separator disposed Within said aperture at a point along the length of said tip intermediate the ends thereof;

a first passage in one side of said separator extending toward the first ends of said ducts and a second passage in the opposite side of said separator extending toward tlleisecond ends of said ducts; an outwardly extending passage in said separator connecting one of said ducts andsaid first passage; another of si si ,reseela ti 7 ends and having a longitudinal axis along the length thereof; 7 e

an inlet port for each of said ducts having a longitudinal axis disposed substantially parallel to the axis of a corresponding duct near the first end thereof;

means connecting one of said inlet ports With a first end of one of said ducts;

said one inlet port being positioned back along the longitiidinal axis of said one duct to provide an inlet at a point along said duct which is intermediate the first and second ends thereof;

oasis connecting another of said inlet ports With a first end of the other of said ducts;

said other inlet port being positioned away from and beyond the first end of said other duct;

. means connecting the inlet ports and the acoustical ducts each including a passage which extends radially outward from the longitudinal axis of said ducts and connects a duct with an inlet port to provide spatially offsetting bends in the ducts having substantially similar acoustical properties; and

means connected to the secondends of said ducts to provide an output in response tothe combination of acoostical signals in said ducts.

References Cited by tlie Examiner UNITED STATES PATENTS 2,455,465 10/49 C lney et al 175 -138X 

1. A ACOUSTICAL APPARATUS COMPRISING: A PAIR OF ACOUSTICAL DUCTS OF SIMILAR LENGTH, EACH HAVING FIRST AND SECOND ENDS; A SOUND-RECEIVING TIP OF ELONGATED SHAPE ATTACHED TO SAID ACOUSTICAL DUCTS, SAID TIP HAVING A LONGITUDINAL AXIS ALIGNED WITH SAID DUCTS AND HAVING A PAIR OF INLET PORTS DISPOSED AT OPPOSITE ENDS THEREOF ALONG SAID AXIS; A FIRST PASSAGE IN SAID TIP EXTENDING TRANSVERSE TO SAID AXIS AND CONNECTING ONE INLET PORT AND THE FIRST END OF ONE OF SAID DUCTS; A SECOND PASSAGE IN SAID TIP EXTENDING TRANSVERSE TO SAID AXIS AND CONNECTING THE OTHER INLET PORT AND THE FIRST END OF THE OTHER OF SAID DUCTS; THE ACOUSTICAL LENGTH OF SAID ONE INLET PORT AND FIRST PASSAGE BEING EQUAL TO THE ACOUSTICAL LENGTH OF SAID OTHER INLET PORT AND SECOND PASSAGE; AND A TRANSDUCER CONNECTED TO THE SECOND END OF SAID DUCTS FOR PRODUCING OUTPUT SIGNALS RELATED TO THE COMBINATION OF ACOUSTICAL SIGNAL APPEARING IN SAID DUCTS. 